RU2738537C1 - Furnace with inclined-pushing grate for burning wood wastes - Google Patents

Abstract

FIELD: devices for incineration of wastes.

SUBSTANCE: invention relates to devices for burning wastes from treatment and processing of woody biomass and can be used in heat engineering. Furnace with inclined-pushing grate comprises combustion chamber separated by arch vault, equipped with fuel feed devices, devices for primary air input by air for grate and secondary air into superlayer volume through horizontal nozzles located on side walls in one inclined plane above second and third zones of grate, and afterburning and cooling chamber connected to combustion chamber by outlet opening, secondary air supply nozzles are located on opposite walls with displacement by half-step relative to nozzles of opposite wall. Outlet opening is located above third zone of inclined-pushing grate and is equipped with collar directed downwards of furnace, under which horizontally opposite-installed two nozzles for inlet of tertiary air, in afterburning and cooling chamber behind outlet opening, in direction of combustion products movement, additional tangential nozzles for tertiary air inlet are installed tangentially in two parallel planes. Under the grate, on the side opposite to the primary air supply, on the side opposite to the primary air supply, recirculation gases are introduced, which are taken from the gas duct after the main smoke exhauster, into the combustion chamber, above the first grate zone, recirculation gases are introduced through horizontally located nozzles on side walls. Note here that nozzles on side wall are installed with offset by half-step relative to nozzles of opposite wall.

EFFECT: invention allows reducing heat losses with outgoing gases, increasing fuel combustion completeness and service life of grate and burnishing of furnace.

1 cl, 4 dwg

Description

The invention relates to a device for the incineration of waste processing and processing of wood biomass and can be used in thermal power engineering.

Known furnaces with oblique-pushing grates, in which fuel from the bunker enters the grate, which is formed from alternating rows of movable and stationary grates, arranged in steps. The angle of inclination of the grate is less than the angle of natural slope of the burnt fuel, and the movement of fuel along the grate occurs due to the reciprocating motion of the movable grate, while the layer is skewed. Air supply under the grate is carried out by zones. [Styrikovich M.A., Katkovskaya K.Ya., Serov E.P. Boiler units. M.-L. Gosenergoizdat, 1959, p. 78].

To reduce heat losses with chemical incompleteness of combustion in furnaces with obliquely pushing grates, they began to use sharp blast nozzles installed on the front and rear walls, which made it possible to somewhat reduce the value of this loss to 2.5-3%. [Dumer A.B. Furnace mechanisms. M.-L. Gosenergoizdat, 1963, p. 92-93].

Known furnaces with obliquely pushing grates for burning wood waste with moderate moisture content (up to 45-50%), in which waste is fed to the grate by screw feeders, primary air is supplied under the grate by zone (three zones), and secondary air is introduced into the furnace the volume above the second and third zones of the grate from the side of the side walls with the help of the horizontal sides of the side walls with the help of the walls complete combustion of fuel in the furnaces from cylindrical nozzles located opposite in the same vertical plane. The number of secondary blast nozzles is determined by the length of the grate and, accordingly, by the heat output of the furnace. High-temperature combustion products in the above-layer region of the combustion chamber move to the first zone of the grate, intensifying the thermal preparation of fresh fuel for ignition, and through the exit window of rectangular cross-section located in the arch-type roof above the end section of the first zone of the grate, they are directed to the afterburning and cooling chamber, in which the combustion process is completed and the flue gases are cooled before they enter the gas-water heat exchanger. [Lyubov V.K., Lyubova N.V. Combustion of biofuels in boilers "Danstoker" // Actual problems of the forestry complex development: Materials of the international scientific and technical conference. Vologda: RIO VoGTU, 2009 p. 105-107]. We have taken this combustion device as a prototype.

However, these furnaces are very sensitive to the particle size distribution of the combusted fuel and changes in its thermal characteristics. With an increase in the composition of the burned fuel of fine fractions, a decrease in its moisture content or the speed of movement along the grate, the ignition zone moves in the direction of the front wall of the furnace. Early ignition of the fuel, accompanied by intense release of volatile substances, in the absence of secondary air supply to this area, causes a significant increase in heat loss with chemical underburning of the fuel and a decrease in the efficiency and reliability of the furnace and the boiler as a whole.

The problem to be solved by the invention is to create a highly efficient low-emission combustion device for burning wood fuel of an extremely heterogeneous particle size distribution (with a particle size that differs by a factor of thousands) with a relative humidity of up to 50-57% per working mass.

This is achieved by the fact that in a furnace with an inclined-pushing grate, containing a combustion chamber separated by an arched vault, equipped with fuel supply devices, devices for introducing primary air under the grate and secondary air into the above-layer volume through horizontal nozzles located on the side walls in one an inclined plane above the second and third zones of the grate, and the afterburner and cooling chamber connected to the combustion chamber by an outlet window, nozzles for supplying secondary air are located on opposite walls with a half-step offset relative to the nozzles of the opposite wall, the outlet window is located above the third zone of oblique-pushing grate and is equipped with a collar directed downward of the furnace, under which two nozzles for entering tertiary air are horizontally oppositely displaced, in the afterburner and cooling chamber outside the outlet window, in the direction of the combustion products are installed tangentially in two x parallel planes additional nozzles for introducing tertiary air, under the grate, in zones from the side opposite to the primary air supply, recirculation gases are introduced, taken from the flue after the main exhaust fan, into the combustion chamber, above the first zone of the grate, through nozzles horizontally located on the side walls , recirculation gases are introduced, while the nozzles on the side wall are installed with a half-step offset relative to the nozzles on the opposite wall.

FIG. 1 shows the proposed firebox, longitudinal section; in fig. 2 is a cross-section a-a of FIG. 1; FIG. 3 is a local horizontal section B-B of Fig. 1; Fig. 4 is a local horizontal section B-B of Fig. 1.

The furnace with an inclined push grate contains combustion chambers 1 and afterburning and cooling 2, separated by an arched vault 3 made of refractory materials, above the third zone of an inclined push grate 4 in the vault 3 there is an outlet window 5 equipped with a collar 6 directed down the furnace , under which two nozzles 7 are installed horizontally oppositely displaced for introducing tertiary air, and in the afterburning and cooling chamber 2 behind the outlet window 5 additional nozzles 8 are installed tangentially in two parallel planes for introducing tertiary air. On the front wall of the furnace, fuel feeders 9 are installed, and on the side walls above the first zone of the inclined-pushing grate 4, nozzles 10 are horizontally located for introducing recirculation gases, and above the second and third zones of the grate there are nozzles for supplying secondary air 11, while the nozzles for introducing gases recirculation 10 and secondary air 11 are displaced by half a step relative to the nozzles of the opposite wall. Secondary air is supplied to the nozzles using air ducts 12, tertiary air using air ducts 13 and recirculation gases using gas ducts 14 laid along the side walls of the combustion chamber 1. The screw conveyor 15, the axis of which is perpendicular to the longitudinal axis of the furnace, is located at the end of the oblique-pushing grate 4. Primary air is supplied under the grate by means of ducts 16 by zones, while recirculation gases are supplied from the opposite side of the furnace zone by zone under the grate, the selection of which is carried out from the flue after the main exhaust fan using a recirculation exhaust fan.

The work of a furnace with an inclined push grate for burning wood waste is carried out as follows.

Polyfractional wood waste from the bunkers by feeders 9 is fed to the inclined pushing grate 4 in the section of the first zone of which thermal preparation and ignition of wood fuel occurs, in the second and third zones, respectively, active combustion and afterburning of the combustible components of the fuel occurs, primary air under the grate the grate with the help of boxes 16 is supplied by space, in an amount less than theoretically required for fuel combustion. To exclude local burnout of the grate and burnout of the lining, from the side opposite to the primary air inlet, part of the recirculation gases are supplied under the grate zone by zone, the selection of which is carried out from the flue after the main exhaust fan using an individual recirculation exhaust fan. Another part of the recirculation gases is introduced into the combustion chamber above the first zone of the inclined-pushing grate 4 through horizontally located nozzles 10 made on the side walls with a half-step offset relative to the nozzles of the opposite wall. The introduction of recirculation gases, the temperature of which is several times higher than the temperature of the supplied air, intensifies the thermal preparation of wood waste for ignition, reduces the emission of nitrogen oxides and expands the capabilities of the furnace in terms of the moisture content of the combusted fuel. The ratio between primary and secondary air is determined by the thermophysical characteristics of the combusted fuel, with an increase in fuel moisture, the proportion of primary air increases, and the proportion of recirculation gases under the grate decreases. The products of incomplete combustion leaving the fuel layer enter the vortex flows formed by the interaction of counter-displaced jets of recirculation gases coming out of the nozzles 10 above the first zone and secondary air exiting the nozzles 11 above the second and third zones of the grate. The vortex flows of hot flue gases also affect the fuel layer located on the grate 4, increasing the uniformity of fuel distribution along its width and increasing the life cycle of the grate. The movement of vortex gas flows from the front to the rear wall of the furnace makes it possible to exclude the possibility of transit removal of unburned gaseous combustible components of the fuel from the combustion chamber, which could take place when the outlet window 5 was located above the first zone of the inclined push grating 4. In the area of the outlet window 5 located in arched vault 3 above the third zone of the grate 4 and equipped with a collar 6, additional swirling of the gas flow is performed when jets of tertiary air are introduced through horizontal counter-displaced nozzles 7. This vortex flow ensures reliable burnout of combustible components coming from the fuel layer, as well as in combination with the collar 6 of the outlet window 5 reduces the removal of the solid phase from the combustion chamber 1 into the afterburner and cooling chamber 2, increasing the boiler company in terms of cleaning. Additional swirling and turbulization of the gas flow in the afterburner and cooling chamber 2, carried out using additional tertiary air nozzles 8 tangentially installed in two parallel planes, intensifies heat transfer in the afterburner and cooling chamber 2, creates conditions for minimizing chemical underburning and the formation of nitrogen oxides and improves conditions operation of the gas-water heat exchanger. Removal of focal residues from the combustion chamber 1 during the operation of the boiler is carried out using a screw conveyor 15.

Studies have shown that this furnace allows for efficient combustion of wood fuel of an extremely inhomogeneous particle size distribution (with a particle size that differs by a factor of thousands), increase the boiler gross efficiency by at least 1.5-2.0% by reducing heat losses with waste gases and with chemical incompleteness of fuel combustion, ensure the ability to work with ultra-low excess air at the outlet from the furnace (α _t = 1.15), reduce emissions of nitrogen oxides ~ 20% and carbon monoxide by 30-50%, as well as extend the life cycle obliquely - pushing grate and firebox lining.

Claims (1)

A furnace with an inclined-pushing grate, containing a combustion chamber separated by an arched vault, equipped with fuel supply devices, devices for introducing primary air under the grate and secondary air into the supra-layer volume through horizontal nozzles located on the side walls in one inclined plane above the second and third zones of the grate, and an afterburner and cooling chamber connected to the combustion chamber by an outlet window, characterized in that the secondary air supply nozzles are located on opposite walls with a half-step offset relative to the nozzles of the opposite wall, the outlet window is located above the third zone of the inclined push grate and equipped with a collar directed downward of the furnace, under which two nozzles for entering tertiary air are horizontally oppositely displaced, in the afterburner and cooling chamber outside the outlet window, in the direction of the combustion products, are installed tangentially in two pa parallel planes additional nozzles for introducing tertiary air, under the grate, in zones from the side opposite to the primary air supply, recirculation gases are introduced, taken from the flue after the main exhaust fan, into the combustion chamber, above the first zone of the grate, through nozzles horizontally located on the side walls, recirculation gases are introduced, while the nozzles on the side wall are installed with a half-step offset relative to the nozzles on the opposite wall.

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